JP3085657U - Tie bar cut die structure with anti-scraping - Google Patents

Abstract

(57) [Problem] To provide a tie bar cut die structure that prevents a dam bar from chipping and rising generated in a tie bar cutting step of a semiconductor package. SOLUTION: From a cutting edge portion on both sides of an upper surface of a block 5 of a tie bar cutting die 7, along a lower surface of the block 5, a cutting edge a1 and a subsequent cutting edge b2 are provided from an end face of the block 5,
At a position where the depth 15 dimension of the cutting blade a1 is at an arbitrary position within a range where the dam bar is actually cut, a cutting blade step 3 (0.0
(Ranging from 0.01 mm to 0.005 mm).

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a structure of a tie bar cut die incorporated in a die used for cutting a dam bar between outer leads in a lead frame of a semiconductor package formed by resin sealing.

[0002]

[Prior art]

 In the manufacturing process of a semiconductor package that requires leads, the semiconductor element is molded and sealed with resin, and thereafter, a trimming process is performed in which a dam bar that connects the outer leads of the semiconductor package is cut off. As shown in FIG. 6, each outer lead 4 of the semiconductor lead frame sealed and molded with the resin 10 is in a state of being connected by the dam bar 9.

In order to cut off the dam bar 9, a semiconductor package is formed by a tie bar in which a block 5 having a cutting edge is formed in a comb blade shape by a grinding process using a blade as shown in FIG. It is carried on the die on which the cut die 7 is mounted. As shown in FIG. 4, blocks 5 are formed on the upper part of the tie bar cutting die 7 so as to protrude like comb teeth in accordance with the pitch of the outer leads, and straight edges on both upper surfaces of each block 5 are cut. The blade 6 is provided. FIG. 5 shows a position state when the semiconductor package molded and sealed with the resin 10 is carried into the tie bar stage of the mold. The outer lead 4 is connected by a dam bar 9, and the center axis of the outer lead 4 is positioned vertically so as to be coaxial with the center axis of the comb-shaped block 5 formed on the upper surface of the tie bar cutting die 7. The tie bar cut punch 8 is positioned in a vertical direction such that the center axis of the punch blade 11 and the center axis between the blocks 5 adjacent to the tie bar cut die 7 are coaxial.

FIG. 7 shows a cut state. FIG. 7A shows a state where the lead frame is set on the tie bar cut die 7. FIG. 7B shows a state where the punch blade 11 has entered the tie bar cut die 7. The clearance 13 between the cutting blade 6 of the tie bar cutting die 7 and the punch blade 11 is usually set in the range of 0.006 mm to 0.015 mm. FIG. 7D shows a state in which the punch blade 11 has entered the tie bar cutting die 7 and chippings 12 have been generated. Usually, the punch blade 11 is provided with a shear angle 14 of 10 to 15 degrees in order to disperse the impact at the time of cutting and to smoothly perform cutting. After the punch blade 11 has entered the position beyond the lower end of the block 5 of the tie bar cutting die 7, the punch blade 11 follows the entered reverse direction and returns to the original position. The chips 12 protruding from the lower surface of the block 5 fall under their own weight, or are sucked by a dust collector provided in the mold and collected outside the mold.

FIG. 8 shows a state of a normal tie bar cut semiconductor package from which a dam bar has been cut. Each outer lead 4 is separated.

[0006]

[Problems to be solved by the invention]

 However, the conventional cutting device has the following problems. The problem will be described with reference to FIG. 7D. When the cutting is performed, the punch blade 11 and the swarf 12 may generate pressure bonding, and the lower surface of the block 5 cannot be dropped by its own weight or sucked by the dust collector. The punch blade 11 passes through the block 5 with the chip 12 attached thereto, and returns to the original dam bar position. FIG. 7C shows a state in which the chip 12 has returned to the outer lead position once cut and has been caught. When this condition occurs, when the mold is engaged in order to cut the tie bars of the next semiconductor package that has been continuously loaded, the chips that have been caught at the outer lead position generated during the previous press are removed. Is pressed and stuck in the outer lead position, and the adjacent outer leads 4 are short-circuited. In this state, it may flow to the final process. Note that this defect short-circuits the leads and can be found in the test process of testing the electrical characteristics. However, in rare cases, the leads that are stuck in the ground may be grounded due to the characteristics of the semiconductor package. If it is designed to have negative polarity, it will not be found in the test process and will be delivered to the customer, and the assembled final product will go to market. If these final products are used by consumers and subjected to impact, etc., chips that get stuck between the leads will be scattered, causing other electronic products to be short-circuited and malfunctioning of the devices. It could lead to an accident. The purpose of the present invention is to solve such problems.

[0007]

[Means for Solving the Problems]

 As a means for solving the above-mentioned problem, as shown in FIG. 2, the present invention relates to a cutting edge portion of the block 5 of the tie bar cutting die 7 which is perpendicular to the lower surface side of the block 5 from the end face of the block 5. A cutting edge b2 is provided, and a cutting edge step 3 (a range of 0.001 mm to 0.005 mm) is provided at a position where the depth 15 of the cutting edge a1 is at an arbitrary position within a range where the dam bar is actually cut. It was to be. The cutting blade a1 and the cutting blade b2 are manufactured by grinding using a blade or electric discharge machining using a wire cut.

[0008]

[Embodiment of the invention]

 FIG. 1 shows an embodiment of the present invention. FIG. 1A shows a state where the lead frame is set on the tie bar cut die 7. The depth 15 dimension of the cutting edge a1 is an arbitrary value that does not exceed the actual cutting edge outer end 17 beyond the actual cutting edge inner end 16 from the end face 5 of the block. And at this depth 15, the cutting edge step 3 of the cutting edge a1 and the cutting edge b2 is provided.

FIG. 1B shows a state where the punch blade 11 has entered the tie bar cut die 7. The clearance 13 between the cutting blade b2 of the tie bar cutting die 7 and the punch blade 11 is in the range of 0.006 mm to 0.010 mm, and the cutting blade a1 is 0.001 mm to 0.005 mm with respect to the cutting blade b2. The step 3 is machined within the range. The clearance between the cutting blade b2 and the punch blade 11 is in the range of 0.007 mm to 0.015 mm as a result.

FIG. 1D shows a state in which the punch blade 11 has entered the tie bar cutting die 7 and chipping 12 has occurred. The punch blade 11 is machined at an arbitrary shear angle 14 within a range of 15 degrees to 30 degrees. When the punch blade 11 enters the tie bar cutting die 7, the dam bar 9 is cut halfway by the cutting blade a 1, and then the remaining dam bar 9 is cut by the cutting blade 2. At this time, the chip 12 tends to be pushed downward while rotating by the punch angle 11 by the shear angle 14. Since the swarf cut by the cutting blade a1 is cut larger than the swarf shape cut by the cutting blade b2 by an amount corresponding to the cutting edge step 3, the swarf cut by the cutting blade a1 is cut. A part of the residue 12 (the black portion) interferes with the wall surface of the cutting edge b2. The cutting by the cutting blade b 2 is completed, and the chip 12 descends while continuing the above-mentioned interference while being supported by the lower surface of the punch blade 11 as the punch blade 11 enters. After descending to a position where several sheets (range of one to three sheets) remain in the section, the punch blade 11 follows the entered reverse direction and rises to the original position. Even when the punch blade 11 starts to ascend, the chip 12 continues to maintain the above-mentioned interference, and the force of the chip 12 to interfere with the wall surface of the cutting blade b 2 causes the chip 12 to be pressed against the lower surface of the punch blade 11. Since the force exceeds the force, the chip 12 from the lower surface of the punch blade 11 is separated from the lower surface of the punch blade 11 when the punch blade 11 starts ascending and remains in a state of interfering with the wall surface of the cutting blade b2.

FIG. 1C shows a state in which the cutting of the dam bar 9 is completed and the chips 12 maintain the interference between the adjacent blocks 5.

[0012]

[Effect of the invention]

 As described above, the use of the tie bar cut die with the structure of the present invention can reliably prevent the chip from rising, and when using an electronic product incorporating a semiconductor package in the market, the distance between the leads is reduced. It is possible to prevent a serious accident in which the embedded chips are scattered, causing a short circuit of the electronic product and causing a malfunction of the device.

[Brief description of the drawings]

FIG. 1 shows an embodiment of claim 1 of the present invention, and FIG. 1A is an enlarged top view showing a state where a lead frame is set on a tie bar cut die 7 of the present invention. FIG. B shows a punch blade 11.
2 is an enlarged top view showing a state in which the tool has entered a tie bar cut die 7. FIG. In FIG. C, the cutting of the dam bar 9 is completed, and
FIG. 2 is an enlarged top view showing a state in which interference is maintained between adjacent blocks 5. FIG. D is an enlarged cross-sectional view taken along the line E-E in FIG. B, showing a state where the punch blade 11 has entered the tie bar cutting die 7 and chips 14 have been generated.

FIG. 2 is an enlarged perspective view of claim 1 of the present invention.

FIG. 3 is a perspective view of a tie bar cut die.

FIG. 4 is an enlarged perspective view showing a cutting edge shape of a conventional tie bar cutting die.

FIG. 5 is a perspective view showing a state before a tie bar is cut, showing a position state when a semiconductor package molded and sealed with a resin 10 is carried into a tie bar stage of a mold.

FIG. 6 is an enlarged top view of a semiconductor package showing a state before a tie bar is cut, and an enlarged side view thereof.

FIG. 7A is an enlarged top view showing a state where a lead frame is set on a conventional tie bar cut die 7. FIG. FIG. 2B is an enlarged top view showing a state where the punch blade 11 has entered the conventional tie bar cutting die 7. FIG. 5C is an enlarged top view showing a state in which the chip 12 returns to the outer lead position once cut and is caught. FIG. 4D is an enlarged cross-sectional view taken along line FF in FIG. 4B, showing a state in which the punch blade 11 has entered the tie bar cutting die 7 and chips 12 have been generated.

FIG. 8 is an enlarged top view of the semiconductor package showing a state where a tie bar has been cut.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cutting blade a 2 Cutting blade b 3 Cutting blade step 4 Outer lead 5 Block 6 Cutting blade 7 Tie bar cut die 8 Tie bar cut punch 9 Dam bar 10 Resin 11 Punch blade 12 Cutting chip 13 Clearance 14 Shear angle 15 Depth 16 Actual cutting blade Edge 17 Actual cutting edge outer edge

Claims (1)

[Utility model registration claims] According to the present invention, a comb frame is formed in a tie bar cut die incorporated in a die used for cutting a dam bar between outer leads in a lead frame of a resin-molded semiconductor package. It is characterized by providing a cutting edge step at any position within the cutting blade range where the dam bar is actually cut from the block end surface, vertically from the dam bar cutting edge portion on both sides of each block toward the lower surface of each block. This is a device relating to the structure of a die to be formed.